تاثیر فنوکسی‌کارب بر پاسخ های ضد ویروسی RNAi و apoptosisدر کرم غوزه پنبه Helicoverpa armigera

Immunity system activated different pathways following viral infection. Intracellular pathways such as RNA interference (RNAi) and apoptosis are the most important immune system responses to viral infection. The effect of juvenile and ecdysone hormones on the immune system has been reported, but the effect of these compounds on the antiviral immune response is unknown. Since viruses are one of the most important agents for biological control of insects, the study of the interaction between antiviral and hormonal factors such as insect growth regulators (IGRs) can provide a safe pest control. Therefore, in this study, the effect of fenoxycarb as an analog of juvenile hormone (JH) on apoptosis and RNA interference (RNAi) pathways, including miRNA and siRNA pathways, in the fat bodies of Helicoverpa armigera larvae have been investigated. For this purpose, third instar larvae (one day old) of H. armigera was exposed to lethal (LC50) and sublethal (LC10, LC25) concentrations of fenoxycarb that were 3.42, 5.43 and 9.12 mg/l respectively. After 24, 48, and 96 hours, the total RNA samples were extracted from the fat bodies of the larvae and then cDNA synthesized using the Oligodt primer. The expression level of Dicer1, Ago1 genes in miRNA and Dicer2, Ago2 pathways in siRNA pathway as well as Caspase1, Caspase5 and, Survivin in the apoptosis pathway were investigated by using qRT-PCR. Rpl27 gene was used as a reference gene. Our results showed that fenoxycarb increased the expression level of miRNA and siRNA pathway genes, while the expression of Caspase1 and Caspase5 genes were significantly decreased. Expression level of Caspase1 and Caspase5, after using the LC50 concentration, reaches its lowest level at all time intervals compared to the control. Expression level of the Survivin gene (regulator of the apoptotic pathway) increases after using all concentrations of fenoxycarb, so that the highest expression of this gene is at the LC50 concentration at all interval times. The highest expression level of apoptosis pathway genes and lowest expression level of negative regulator of this pathway was observed in 48 hours exposure to fenoxycarb. Together, it can be concluded that using of JH hormone analog compounds can inhibit the apoptosis pathway that is the most important antiviral response of the insects and activate the RNAi pathway.